Melting and mechanical properties of polymer grafted lipid bilayer membranes

Abstract

The influence of polymer grafting on the phase behavior and elastic properties of two tail lipid bilayers have been investigated using dissipative particle dynamics simulations. For the range of polymer lengths studied, the L(c) to L(α) transition temperature is not significantly affected for grafting fractions, G(f) between 0.16 and 0.25. A decrease in the transition temperature is observed at a relatively high grafting fraction, G(f) = 0.36. At low temperatures, a small increase in the area per head group, a(h), at high G(f) leads to an increase in the chain tilt, inducing order in the bilayer and the solvent. The onset of the phase transition occurs with the nucleation of small patches of thinned membrane which grow and form continuous domains as the temperature increases. This region is the co-existence region between the L(β)(thick) and the L(α)(thin) phases. The simulation results for the membrane area expansion as a function of the grafting density conform extremely well to the scalings predicted by self-consistent mean field theories. We find that the bending modulus shows a small decrease for short polymers (number of beads, N(p) = 10) and low G(f), where the influence of polymer is reduced when compared to the effect of the increased a(h). For longer polymers (N(p) > 15), the bending modulus increases monotonically with increase in grafted polymer. Using the results from mean field theory, we partition the contributions to the bending modulus from the membrane and the polymer and show that the dominant contribution to the increased bending modulus arises from the grafted polymer.

Morphological changes of amphiphilic molecular assemblies induced by chemical reactions

“…Dissipative Particle Dynamics (DPD) is a coarsegrained molecular simulation method to take into account hydrodynamic interactions [18][19][20]. The DPD method is applied to complex fluids such as amphiphilic molecules [15,[21][22][23][24][25][26][27][28][29][30] and polymers [20,[31][32][33]. In this method, several atoms are coarse-grained into one DPD particle, so long-term simulation can be performed compared to atomic-scale molecular dynamics.…”

A generic force field for simulating native protein structures using dissipative particle dynamics

“…41,42 DPD has been extensively used to study biomembranes, polymers and polyelectrolytes, and it has been shown to predict the scaling behaviour of several systems. [43][44][45][46][47][48][49][50][51] However, DPD has been used to a lesser extent to study systems involving peptides and proteins. The DPD simulation framework is attractive for the simulation of proteins, since dynamics are naturally evolved in the canonical ensemble in the presence of explicit solvent particles.…”

A Generic Force Field for Simulating Native Protein Structures Using Dissipative Particle Dynamics

“…41,42 DPD has been extensively used to study biomembranes, polymers and polyelectrolytes, and it has been shown to predict the scaling behaviour of several systems. [43][44][45][46][47][48][49][50][51] However, DPD has been used to a lesser extent to study systems involving peptides and proteins. The DPD simulation framework is attractive for simulation of proteins, since dynamics are naturally evolved in the canonical ensemble in the presence of explicit solvent particles.…”